The present invention relates generally to safety systems for syringes, and more particularly to a needle guard for a syringe that includes an automatically activated shield for covering a needle of the syringe.
Medication is often dispensed using a medicine cartridge, such as a syringe, having a barrel with a needle at one end and a plunger slidably inserted into the other end. Such cartridges are often referred to as xe2x80x9cpre-filled syringesxe2x80x9d because they may contain a specific dosage or volume of medication when they are initially provided, as compared to conventional syringes that are furnished empty and filled by the user before making an injection.
Alternatively, a medicine cartridge may be used, such as an ampoule or vial, that includes a penetrable seal instead of a needle on one end of the barrel, and/or a piston rather than a plunger on the other end. Such medicine cartridges are generally inserted into an adapter that includes a hollow body adapted to hold the cartridge, a plunger to engage and move the piston in the cartridge, and/or a double-ended needle to penetrate the seal and communicate with the interior of the barrel.
Because of the risk of communicable diseases, a number of syringes and adapters have been developed that are intended to prevent accidental needle sticks and/or inadvertent reuse of a syringe. Retractable needle devices have been suggested for this purpose that include a cartridge that allows a needle of the cartridge to be withdrawn into the barrel after medication is dispensed from it. For example, U.S. Pat. No. 4,973,316 issued to Dysarz discloses a syringe including a barrel having a needle assembly that is slidable within the barrel between an exposed position such that a needle on the assembly extends from the barrel and a retracted position wherein the needle assembly is withdrawn into the barrel. The needle assembly is initially locked in the exposed position, but may be disengaged upon depression of the plunger, whereupon a spring biases the assembly towards the retracted position, thereby withdrawing the needle into the barrel.
Other retractable devices have been suggested that include special plungers that may capture or otherwise engage a needle assembly upon full depression of the plunger, the needle assembly being manually or automatically withdrawn into the barrel, for example, by subsequently retracting the plunger or by a spring within the barrel. Generally, these retractable needle devices require specially designed cartridges that are substituted for a conventional syringe, and may not be used to hold commercially available pre-filled syringes or ampoules.
In addition to retractable devices, extendable needle guard devices have been suggested that include a shield that is attachable to a needle hub of a syringe or cartridge adapter. The shield may be slidable, for example, from a retracted position, coextensive with the syringe barrel such that the needle is exposed, to an extended position, covering the needle. The shield may be advanced manually between the retracted and extended positions, and may be lockable in the extended position. Alternatively, the needle guard may include a spring that automatically extends the shield to cover the needle, for example, when released by an actuator on the device. These needle guards, however, generally require specially configured needle hubs or barrels on the syringe to accommodate the attachment of the shield, and may not be used with conventional syringes or cartridges.
Alternatively, syringe holders have been suggested that include a body within which a conventional syringe or cartridge may be received, and a shield that is manually slidable with respect to the body to cover the needle. For example, U.S. Pat. No. 6,030,366, issued to Mitchell, which is assigned to the assignee of the present application, discloses a self-shielding guard that includes a body having an open proximal end for inserting a syringe into a cavity within the body, and a distal end with an opening through which a needle on the syringe may extend once received in the body. A shield is slidable over the body between retracted and extended positions to expose and cover the needle, respectively. With the shield in the retracted position and the needle exposed, an injection may be made, and then the shield may be manually advanced to the extended position. In the extended position, cooperating detents and detent pockets on the body and shield substantially permanently lock together, thereby preventing reuse of the needle, reducing the risk of accidental needle sticks, and/or facilitating disposal of the syringe.
As an alternative to requiring manual extension of a shield to cover a needle, spring-loaded devices have also been suggested. These devices often include a body and slidable shield, similar to the manual devices described above, but also may include a spring mechanism to bias the shield to advance and cover the needle. An actuator, such as a button or lever, may be activated by the user to release the shield, thereby allowing the spring mechanism to advance the shield to cover the needle. For example, U.S. Pat. No. 5,695,475 issued to Best, Jr. et al. and U.S. Pat. No. 4,923,447 issued to Morgan disclose spring-loaded syringe devices that include inner and outer sliding sleeves that include a button slidable in a longitudinal slot to selectively expose and cover a needle on the devices. A spring in the devices biases one of the sleeves to extend and cover the needle, but this bias may be manually overcome to expose the needle. Thus, these devices may not lock the extending sleeve in a covered position, and therefore may risk accidental needle exposure and/or reuse of the needle. In addition, although these devices are spring-driven, their shields may not extend unless they are manually activated, and therefore are not truly xe2x80x9cpassive,xe2x80x9d but require an affirmative decision by a user to activate their safety feature.
Accordingly, it is believed that a syringe device that automatically activates a needle shield during or following an injection would be considered useful.
The present invention is directed to needle guards for a medicine cartridge, such as a pre-filled syringe, that includes an automatically activated shield for covering a needle of the cartridge, and to methods of making and using such needle guards. In accordance with one aspect of the present invention, a passive needle guard is provided that includes a body having proximal and distal ends and a cavity therein for receiving a medicine cartridge. A shield having proximal and distal ends is attached to the body and slidable between a retracted position for exposing a needle extending from the body, and an extended position for substantially covering the needle, the shield being biased to advance towards the extended position.
Cooperating catches are provided on the body and shield for engaging one another to hold the shield in the retracted position. One or more latch members extend proximally from the proximal end of one of the shield and the body, the latch members being deflectable for disengaging the cooperating catches upon depression of a plunger coupled to the medicine cartridge, whereby the shield may automatically advance to the extended position. Preferably, the cooperating catches include a first catch on respective latch members and a second catch on the body, the latch members being resiliently deflectable radially outwardly for disengaging the first catch from the second catch. More preferably, the latch members are elongate fingers having a proximal tip that is engageable by the plunger as it is depressed to axially compress and deflect the latch members radially outwardly.
The passive needle guard also preferably includes a spring mechanism coupled to the body and the shield for biasing the shield towards the extended position. The spring mechanism may be a compression spring disposed between the body and the shield, for example, disposed concentrically within the shield adjacent to one end of the body or within elongate passages defined by the shield and/or body. Alternatively, an extension spring may be provided with respective ends attached to the shield and body. The spring mechanism may have a nonlinear spring rate such that the spring rate when the shield is in the retracted position is substantially less than the spring rate as the shield approaches the extended position.
In a preferred embodiment, the passive needle guard also includes cooperating detents on the shield and the body that are configured for engaging one another when the shield is disposed in the extended position to prevent retraction of the shield from the extended position. In addition, the passive needle guard may include a locking mechanism on the proximal end of the body, such as locking detents on a finger grip thereof, for substantially securing a medicine cartridge in the cavity.
A medicine cartridge, such as a pre-filled syringe, may be pre-assembled within the passive needle guard, or inserted by a user before making an injection. The medicine cartridge preferably includes a barrel having a needle extending from its distal end and a plunger slidably received in its proximal end. The plunger includes a radial portion for engaging the latch member when the plunger is depressed distally into the medicine cartridge. The radial portion may be provided on an intermediate region of the plunger, or may simply be a thumb pad on a proximal end of the plunger.
To assemble the passive needle guard, the proximal end of the shield may be directed over the distal end of the body. The shield may be directed towards the proximal end of the body from an extended position wherein the distal end of the shield extends beyond the distal end of the body towards a retracted position wherein the distal end of the shield is substantially coextensive with the distal end of the body. A spring may be coupled between the body and the shield, the spring biasing the shield to advance towards the extended position. The latch members on the shield may be deflected radially outwardly as the shield is directed to the retracted position to avoid contact between the catches. The latch members may then be released once the shield has attained the retracted position, the catches on the latch members engaging the catches on the body to substantially secure the shield in the retracted position.
A medicine cartridge may be inserted into the cavity in the body, preferably axially into the proximal end of the body until a locking mechanism on the body engages the medicine cartridge to substantially permanently lock the medicine cartridge therein. The latch members may need to be deflected radially outwardly as the medicine cartridge is inserted into the body, while retaining the shield in the retracted position, to accommodate a flange on the medicine cartridge. Alternatively, the cartridge may be inserted into the body before the shield is fully retracted, thereby avoiding any possible contact between the latches and a flange on the cartridge.
The passive needle guard and cartridge may then be used to perform an injection. The needle may be inserted into a patient with the shield retained in the retracted position by the cooperating catches. A plunger communicating with the medicine cartridge may be depressed to inject medication into the patient until the plunger engages the latch members extending from the passive needle guard. The plunger may then be depressed further to deflect the latch members radially to disengage the cooperating catches, and release the shield, whereupon the shield may automatically advance towards the extended position. Thus, because of the latch members and cooperating catches, the shield may be automatically activated and advanced without requiring any action from the user other than depression of the plunger, thereby providing a needle guard device that is truly passive. The needle may then be withdrawn from the patient, the released shield automatically advancing fully to the extended position to cover the needle.
When the shield is advanced to the extended position, the cooperating detents on the shield and body preferably engage one another, thereby preventing subsequent proximal movement of the shield. Thus, the shield may be substantially permanently locked in the extended position, preventing inadvertent reuse of the cartridge, minimizing the risk of accidental needle sticks, and/or facilitating safe disposal of the cartridge.